Film-forming compositions having improved scratch resistance

ABSTRACT

Multi-component composite coating compositions are provided which comprise a base coat deposited from a pigmented film-forming composition and a transparent top coat applied over the base coat in which the transparent top coat is deposited from a film-forming composition comprising one or more ungelled chain-extended organic polysiloxanes having reactive functional groups, and one or more curing agents having functional groups reactive with the functional groups of the polysiloxane. Additionally provided is a process for applying the multi-component composite coatings described above to a substrate. Substrates coated with the above-described multi-component composite coating compositions are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-in-Part application of U.S. patentapplication Ser. Nos. 08/986,812 filed Dec. 8, 1997, now U.S. Pat. No.6,033,545 and 08/904,597 filed Aug. 1, 1997, now U.S. Pat. No.5,939,491.

FIELD OF THE INVENTION

The present invention relates to curable compositions, particularly tocurable film-forming compositions, comprising a functionalgroup-containing organic polysiloxane component, which is achain-extended reaction product, the compositions being characterized inthat they provide cured compositions having high crosslink densities.More particularly, the invention relates to curable film-formingcompositions which exhibit improved scratch resistance.

BACKGROUND OF THE INVENTION

Color-plus-clear coating systems involving the application of a coloredor pigmented base coat to a substrate followed by application of atransparent or clear top coat over the base coat have becomeincreasingly popular as original finishes for automobiles. Thecolor-plus-clear systems have outstanding appearance properties such asgloss and distinctness of image due in large part to the clear coat.

Clear film-forming compositions, particularly those used to form thetransparent top coat in color-plus-clear systems for automotiveapplications, are subject to damage from numerous environmentalelements. Such elements include acidic precipitation, exposure toultraviolet radiation from sunlight, high relative humidity andtemperatures, and defects due to impact with small, hard objectsresulting in chipping and scratching of the coating surface.

Typically, a harder more highly crosslinked film may exhibit improvedscratch resistance, but it is much more susceptible to chipping and/orthermal cracking due to embrittlement of the film resulting from a highcrosslink density. A softer, less crosslinked film, while not prone tochipping or thermal cracking, is susceptible to scratching, waterspotting and acid etch due to a low crosslink density of the cured film.

U.S. patent Ser. No. 08/904,597, filed Aug. 1, 1997 discloses curablecompositions based on functional polysiloxanes, particularly hydroxylfunctional group-containing polysiloxanes, which are suitable for use asclear coats in color-plus-clear systems for automotive applications. Thefunctional group-containing polysiloxanes provide clear coatings with,inter alia, improved mar and acid etch resistance.

U.S. Pat. No. 5,853,809 discloses clear coats in color-plus-clearsystems which have improved scratch resistance due to the inclusion inthe coating composition of surface reactive inorganic microparticlessuch as colloidal silicas which have been modified with a reactivecoupling agent. There, nonetheless, remains a need in the automotivecoatings art for top coats having improved initial scratch resistance aswell as enhanced post-weathering (“retained”) scratch resistance withoutembrittlement of the film due to the high crosslink density.

SUMMARY OF THE INVENTION

In accordance with the present invention, multi-component compositecoating compositions are provided which comprise a base coat depositedfrom a pigmented film-forming composition and a transparent top coat, ortop coats, applied over the base coat in which the transparent top coatis deposited from a film-forming composition comprising:

(a) one or more ungelled organic polysiloxanes having reactivefunctional groups, said polysiloxane comprising at least one unit of thefollowing structure (I):

 wherein R¹ and R² are independently selected from the group consistingof OH and monovalent hydrocarbon groups; X is an organic polyvalentlinking group selected from the group consisting of alkylene,oxyalkylene, and alkylene aryl, which is derived from a material havingtwo or more unsaturated bonds capable of undergoing hydrosilylationreaction; and n has a value ranging from 2 to 4 such that n is equal tothe number of unsaturated bonds capable of undergoing hydrosilylationreaction; and

(b) one or more curing agents having functional groups reactive with thefunctional groups of (a). A method for applying the multi-componentcomposite coating composition to a substrate and coated substrates arealso provided.

Other than in the operating examples, or where otherwise indicated, allnumbers expressing quantities of ingredients, reaction conditions, andso forth used in the specification and claims are to be understood asbeing modified in all instances by the term “about”. Also, as usedherein, the term “polymer” is meant to refer to oligomers and bothhomopolymers and copolymers.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As aforementioned, the transparent top coat of the multi-componentcomposite coating of the present invention is deposited from afilm-forming composition comprising: (a) an ungelled organicpolysiloxane having reactive functional groups of the formula (I) above;and (b) a curing agent having functional groups reactive with thefunctional groups of the polysiloxane (a).

Preferably, the polysiloxane (a) comprises the ungelled reaction productof the following reactants (i) and (ii):

(i) one or more polysiloxanes containing silicon hydride having thestructure (II):

 wherein the R groups are independently selected from the groupconsisting of H, OH, and monovalent hydrocarbon groups connected to thesilicon atoms, provided at least one of the groups represented by R isH; and m has a value ranging from 0 to 100, preferably 0 to 5, such thatthe mole percent of hydrogen-bonded silicon atoms to non-hydrogen-bondedsilicon atoms ranges from 10 to 100; and

(ii) one or more materials having two or more, preferably two,unsaturated bonds capable of undergoing hydrosilylation reaction withthe silicon hydride group (Si—H) of the polysiloxane. Preferably,reactant (ii) contains functional groups, most preferably, hydroxylfunctional groups.

By “ungelled” is meant that the reaction products are substantially freeof crosslinking and have an intrinsic viscosity when dissolved in asuitable solvent, as determined, for example, in accordance withASTM-D1795 or ASTM-D4243. The intrinsic viscosity of the reactionproduct is an indication of its molecular weight. A gelled reactionproduct, on the other hand, since it is of essentially infinitely highmolecular weight, will have an intrinsic viscosity too high to measure.

It should be appreciated that the various R groups can be the same ordifferent and it is usually the case that the R groups will be mixedgroups or entirely monovalent hydrocarbon groups.

As used herein and in the claims, “monovalent hydrocarbon groups” meansorganic groups containing essentially carbon and hydrogen. Thehydrocarbon groups can be branched or unbranched, aliphatic, aromatic,cyclic, or acyclic and can contain from 1 to 24 (in the case of aromaticfrom 3 to 24) carbon atoms. The hydrocarbon groups can be substitutedwith heteroatoms, for example, oxygen. Examples of such monovalenthydrocarbon groups include alkyl, alkoxy, aryl, alkaryl or alkoxyarylgroups.

By “alkylene” is meant acyclic or cyclic alkylene groups having a carbonchain length of from C₂ to C₂₅. Examples of suitable alkylene groupsinclude those derived from propene, butene, pentene, 1-decene, isoprene,myrcene, and 1-heneicosene. By “oxyalkylene” is meant an alkylene groupcontaining at least one ether oxygen atom and having a carbon chainlength of from C₂ to C₂₅, preferably from C₂ to C₄. Examples of suitableoxyalkylene groups include those derived from trimethylolpropanemonoallyl ether, pentaerythritol monoallyl ether, trimethylolpropanediallylether, polyethoxylated allyl alcohol, and polypropoxylated allylalcohol. By “alkylene aryl” is meant an acyclic alkylene groupcontaining at least one aryl group, preferably phenyl, and having analkylene carbon chain length of from C₂ to C₂₅. The aryl group can besubstituted, if desired. Suitable substituent groups include hydroxyl,benzyl, carboxylic acid, and aliphatic groups. Examples of suitablealkylene aryl groups include those derived from styrene and3-isopropenyl-α,α-dimethylbenzyl isocyanate.

It should be understood that the ratio of reactants (i) and (ii) andreaction conditions are selected to produce a “chain extended”polysiloxane reaction product. The term “chain extended” as used hereinis intended to mean that two or more organic polysiloxanes containingsilicon hydride are linked or co-polymerized between at least one Si—Hgroup of one polysiloxane containing silicon hydride and a Si—H group ofanother via a hydrosilylation reaction with a material having two ormore unsaturated bonds capable of undergoing hydrosilylation reaction.To control molecular weight and prevent formation of a gelled reactionproduct, a material having only one unsaturated bond capable ofundergoing hydrosilylation reaction is usually included as a reactant toserve as a “chain terminator”. Examples of such materials which aresuitable for use in the present invention include trimethylol propanemonoallyl ether, pentaerythritol monoallyl ether, vinyl cyclohexanediol, styrene, and the like. Alternatively, to control molecular weightand to prevent formation of a gelled reaction product, a material havingonly one Si—H bond capable of undergoing hydrosilylation reaction can beincluded to serve as a “chain-terminator”. Examples of suitablematerials having only one Si—H capable of undergoing hydrosilylationreaction include trimethylsilane, triphenylsilane, andbis(trimethylsiloxy)methyl silane.

Preparation of the chain-extended organic polysiloxane typically iscarried out in the following manner. An admixture of the material havingonly one unsaturated bond capable of undergoing hydrosilylation reactionand the material having at least two unsaturated bonds capable ofundergoing hydrosilylation reaction is added to a reaction vesselequipped with a means for maintaining a nitrogen blanket. Addedconcurrently is approximately 25 to 75 ppm sodium bicarbonate or metalacetate salt to inhibit possible undesirable side reactions such asthose associated with acetal condensation via a propenyl ether moiety.The temperature is increased to 75° to 80° C. under nitrogen, at whichtime 50 to 65 percent of the total amount of polysiloxane containingsilicon hydride is added under agitation. A catalyst such as atransition metal, for example, nickel and/or salts thereof, iridiumsalts and, more preferably, a Group VIII noble metal, usually, platinumin the form of chloroplatinic acid, is then added and the reactionmixture is allowed to exotherm to 85° C. Generally, the exotherm can becontrolled by adjusting rates of addition of the reactants. Addition ofthe remainder of the polysiloxane containing silicon hydride iscompleted as the reaction temperature is maintained at about 80° to 85°C. The chain-extension reaction is monitored by infrared spectroscopyfor disappearance of the silicon hydride adsorption band (Si—H: 2150cm⁻¹).

Alternatively, the material having only one unsaturated bond capable ofundergoing hydrosilylation reaction and the material having at least twounsaturated bonds capable of undergoing hydrosilylation reaction areadded as separate reactants. The former is added initially and isreacted with 50 to 65 percent of the total amount of polysiloxanecontaining silicon hydride in the presence of the catalyst. The ratio ofthese two reactants is selected such that, subsequent to hydrosilylationreaction, there remains an amount of unreacted Si—H available forsubsequent chain-extension reaction. The material having at least twounsaturated bonds capable of undergoing hydrosilylation reaction is thenadded, and then addition of the remainder of the polysiloxane containingsilicon hydride is completed as the reaction temperature is maintainedat about 80° to 85° C. The chain-extension reaction is monitored byinfrared spectroscopy for disappearance of the silicon hydrideadsorption band.

In a preferred multi-component composite coating compositions of theinvention, the equivalent ratio of Si—H to total unsaturation capable ofundergoing hydrosilylation reaction ranges from 0.5 to 2:1.

It also should be noted that the level of unsaturation contained inreactant (ii) above, is selected to ensure an ungelled reaction productcontaining at least one unit of the structure (I) above. In other words,when a polysiloxane containing silicon hydride having a higher averagevalue of Si—H functionality is used, reactant (ii) should have a lowerlevel of unsaturation. For example, in a preferred embodiment of theinvention, the polysiloxane containing silicon hydride (i) is a lowmolecular weight material where m ranges from 0 to 5 and the averagevalue of Si—H functionality is approximately two. In this case, reactant(ii) can contain two or more, unsaturated bonds capable of undergoinghydrosilylation reaction without the occurrence of gelation.

Examples of the preferred polysiloxane containing silicon hydrideinclude 1,1,3,3-tetramethyl disiloxane where m is 0 and the average Si—Hfunctionality is two; and the polymethyl polysiloxane containing siliconhydride, where m ranges from 4 to 5 and the average Si—H functionalityis about two, commercially available from BASF Corporation as MASILWAXBASE. Preferably, reactant (ii) contains at least two unsaturated bondsin the terminal position.

In a preferred embodiment, the reactive functional groups of thepolysiloxane (a) are provided by reactant (ii) above. The reactivefunctional groups of the polysiloxane (a) are typically selected fromthe group consisting of hydroxyl, carbamate, urea, urethane,alkoxysilane, epoxy, isocyanate and blocked isocyanate and carboxylicacid functional groups. Hydroxyl and/or carbamate group-containingpolysiloxanes are preferred.

To provide polysiloxanes having hydroxyl functional group, preferredmaterials for use as reactant (ii) above include hydroxyl functionalgroup-containing polyallyl ethers such as those selected from the groupconsisting of trimethylolpropane diallyl ether, pentaerythritol diallylether, pentaerythritol triallyl ether and mixtures thereof.Trimethylolpropane diallyl ether is preferred. Mixtures of suchpolyallyl ethers with monoallyl ethers or alcohols are suitable as well.Reaction conditions and the ratio of reactants (i) and (ii) are selectedso as to form the desired functional group.

Typically, the polysiloxane containing hydroxyl functional groups has ahydroxyl equivalent weight of at least 1000 grams per equivalent,preferably at least 500 grams per equivalent, and more preferably atleast 250 grams per equivalent. The polysiloxane containing hydroxylfunctional groups also typically has a hydroxyl equivalent weight ofless than 1000 grams per equivalent, more preferably less than 500 gramsper equivalent, and more preferably 250 grams per equivalent. Thehydroxyl equivalent weight of the polysiloxane containing hydroxylfunctional groups can range between any combination of these valuesinclusive of the recited values.

In another preferred embodiment of the invention, the polysiloxane (a)contains carbamate functional groups and, preferably, comprises theungelled reaction product of the following reactants:

(i) one or more polysiloxanes containing silicon hydride of structure(II) above where R and m are as described above for that structure;

(ii) one or more hydroxyl functional group-containing materials havingtwo or more unsaturated bonds capable of undergoing hydrosilylationreaction as described above; and

(iii) one or more low molecular weight carbamate functional materials,preferably comprising the reaction product of an alcohol or glycol etherand a urea.

The carbamate functional groups typically are incorporated into thepolysiloxane by reacting the hydroxyl functional group-containingpolysiloxane with the low molecular weight carbamate functional materialvia a “transcarbamylation” process. The low molecular weight carbamatefunctional material, which is derived from an alcohol or glycol ether,reacts with the free hydroxyl groups of the polysiloxane, yielding acarbamate functional polysiloxane and the original alcohol or glycolether. Reaction conditions and the ratio of reactants (i), (ii), and(iii) are selected so as to form the desired groups.

The low molecular weight carbamate functional material is usuallyprepared by reacting the alcohol or glycol ether with urea in thepresence of a catalyst such as butyl stannoic acid. Suitable alcoholsinclude lower molecular weight aliphatic, cycloaliphatic, and aromaticalcohols, for example, methanol, ethanol, propanol, butanol,cyclohexanol, 2-ethylhexanol, and 3-methylbutanol. Suitable glycolethers include ethylene glycol methyl ether and propylene glycol methylether. Propylene glycol methyl ether is preferred. The incorporation ofcarbamate functional groups into the polysiloxane can also be achievedby reacting isocyanic acid with the free hydroxyl groups of thepolysiloxane.

As aforementioned, in addition to or in lieu of hydroxyl and/orcarbamate functional groups, the polysiloxane (a) can contain otherreactive functional groups such as epoxy, isocyanate, and carboxylicacid functional groups. To form polysiloxanes containing epoxyfunctional groups, a polysiloxane containing hydroxyl functional groupsas described above is further reacted with a polyepoxide. Thepolyepoxide is preferably an aliphatic or cycloaliphatic polyepoxide ormixtures thereof. Examples of polyepoxides suitable for use in thepresent invention include epoxy functional acrylic copolymers preparedfrom at least one ethylenically unsaturated monomer having at least oneepoxy group, for example, glycidyl (meth)acrylate and allyl glycidylether, and one or more ethylenically unsaturated monomers which have noepoxy functionality. The preparation of such epoxy functional acryliccopolymers is described in detail in U.S. Pat. No. 4,681,811 at column4, line 52 to column 5, line 50, incorporated herein by reference.Reaction conditions and the ratio of reactants are selected so as toform the desired functional groups.

Isocyanate functional group-containing polysiloxanes typically areprepared by reacting a polysiloxane containing hydroxyl functionalgroups, as described above, with a polyisocyanate, preferably adiisocyanate. Examples of suitable polyisocyanates include aliphaticpolyisocyanates, particularly aliphatic diisocyanates, for example1,4-tetramethylene diisocyanate and 1,6-hexamethylene diisocyanate;cycloaliphatic polyisocyanates, for example, 1,4-cyclohexyldiisocyanate, isophorone diisocyanate and α,α-xylylene diisocyanate; andaromatic polyisocyanates, for example, 4,4′-diphenylmethanediisocyanate, 1,3-phenylene diisocyanate, and tolylene diisocyanate.These and other suitable polyisocyanates are described in more detail inU.S. Pat. No. 4,046,729 at column 5, line 26 to column 6, line 28,incorporated herein by reference. Preferred are aliphatic orcycloaliphatic diisocyanates or mixtures thereof. Reaction conditionsand the ratio of reactants are selected so as to form the desiredfunctional groups.

Carboxylic acid functional group-containing polysiloxane, typically areprepared by reacting a polysiloxane containing hydroxyl functionalgroups, as described above, with a polycarboxylic acid or anhydride,preferably an anhydride. Examples of polycarboxylic acids suitable foruse in the present invention include adipic acid, sebacic acid anddodecanedioic acid. Examples of anhydrides suitable for use in thepresent invention include hexahydrophthalic anhydride,methylhexahydrophthalic anhydride, phthalic anhydride, trimelliticanhydride, succinic anhydride, chlorendic anhydride, alkenyl succinicanhydride, and substituted alkenyl anhydride such as octenyl succinicanhydride and mixtures thereof. Reaction conditions and the ratio ofreactants are selected so as to form the desired functional groups.

The polysiloxane containing reactive functional groups (a) typically ispresent in the film-forming compositions of the present invention in anamount of at least 2 to 90 percent by weight, preferably at least 20 to80 percent by weight, and more preferably at least 40 to 60 percent byweight based on the total weight of resin solids in the film-formingcomposition. The polysiloxane containing reactive functional groups (a)is also typically present in the film-forming compositions of thepresent invention in an amount less than 90 to 2 percent by weight,preferably less than 80 to 20 percent by weight, and more preferablyless than 60 to 40 percent by weight based on the total weight of resinsolids in the film-forming compositions. The amount of the polysiloxanecontaining reactive functional groups (a) present in the film-formingcompositions of the invention can range between any combination of thesevalues inclusive of the recited values.

As discussed above, besides the polysiloxane containing reactivefunctional groups (a), the film-forming compositions of the inventioncomprise (b) one or more curing agents having functional groups whichare reactive with the functional groups of the polysiloxane (a).Non-limiting examples of suitable curing agents include aminoplasts,polyisocanates, triazines, polyepoxides, polyacids, and polyols. Whereappropriate, mixtures of these curing agents can be used.

Preferably, the curing agent (b) is an aminoplast. Aminoplast resins,which include phenoplasts, as curing agents for hydroxyl, carboxylicacid, and carbamate functional group-containing materials are well knownin the art. Aminoplasts are obtained from the condensation reaction offormaldehyde with an amine or amide. Preferred amines or amides includemelamine, urea, or benzoguanamine. However, condensates with otheramines or amides can be used; for example, aldehyde condensates ofglycoluril, which give a high melting crystalline product useful inpowder coatings. While the aldehyde used is most often formaldehyde,other aldehydes such as acetaldehyde, crotonaldehyde, and benzaldehydecan be used.

The aminoplast contains imino and methylol groups and preferably atleast a portion of the methylol groups are etherified with an alcohol tomodify the cure response. Any monohydric alcohol can be employed forthis purpose including methanol, ethanol, n-butyl alcohol, isobutanol,and hexanol, with methanol, n-butyl alcohol, and isobutanol beingpreferred.

Preferred aminoplasts include melamine-, urea-, orbenzoguanamine-formaldehyde condensates, preferably monomeric, and atleast partially etherified with one or more alcohols containing from oneto four carbon atoms. Suitable aminoplast resins are commerciallyavailable from Cytec Industries under the trademark CYMEL and fromSolutia, Inc. under the tradename RESIMENE.

The aminoplast curing agent is typically present in the film-formingcomposition in amounts ranging from 5 to 75, preferably from 20 to 60percent, and more preferably from 40 to 60 percent by weight based onthe total weight of resin solids in the film-forming composition.

Other curing agents suitable for use in the film-forming compositions ofthe present invention include polyisocyanate curing agents, for example,capped polyisocyanates. The polyisocyanate can be an aliphatic or anaromatic polyisocyanate or a mixture of the two. Diisocyanates can beused, although higher polyisocyanates such as isocyanurates ofdiisocyanates are preferred. Higher polyisocyanates can also be used incombination with diisocyanates. Isocyanate prepolymers, for example,reaction products of polyisocyanates with polyols can also be used.

If the polyisocyanate is capped, any suitable aliphatic, cycloaliphatic,or aromatic alkyl monoalcohol known to those skilled in the art can beused as a capping agent for the polyisocyanate. Other suitable cappingagents include oximes and lactams. When used, the polyisocyanate curingagent is present in an amount ranging from 5 to 65 percent, preferablyfrom 10 to 45 percent, and more preferably from 15 to 40 percent byweight based on the total weight of resin solids in the film-formingcomposition.

Useful adjuvant curing agents include triazines such as the tricarbamoyltriazine compounds which are described in detail in U.S. Pat. No.5,084,541 which is incorporated herein by reference. When used, theadjuvant triazine curing agent is present in the film-formingcomposition in an amount ranging up to about 20, and preferably fromabout 1 to 20, percent by weight based on the total weight of resinsolids in the film-forming composition.

Anhydrides as curing agents for hydroxyl functional group-containingmaterials are also well known in the art. Anhydrides suitable for use ascuring agents in the film-forming compositions of the invention includethose having at least two carboxylic acid anhydride groups per moleculewhich are derived from a mixture of monomers comprising an ethylenicallyunsaturated carboxylic acid anhydride and at least one vinyl co-monomer,for example, styrene, alpha-methyl styrene, vinyl toluene, and the like.Examples of suitable ethylenically unsaturated carboxylic acidanhydrides include maleic anhydride, citraconic anhydride, and itaconicanhydride, with maleic anhydride being preferred. Alternatively, theanhydride can be an anhydride adduct of a diene polymer, such as,maleinized polybutadiene or a maleinized copolymer of butadiene, forexample, a butadiene/styrene copolymer. These and other suitableanhydride curing agents are described in U.S. Pat. No. 4,798,746 atcolumn 10, lines 16-50; and in U.S. Pat. No. 4,732,790 at column 3,lines 41-57, both incorporated herein by reference.

Polyepoxides as curing agents for carboxylic acid functionalgroup-containing materials are well known in the art. Examples ofpolyepoxides suitable for use in the film-forming compositions of theinvention include polyglycidyl ethers of polyhydric phenols and ofaliphatic alcohols which can be prepared by etherification of thepolyhydric phenol or aliphatic alcohol with an epihalohydrin such asepichlorohydim in the presence of alkali. These and other suitablepolyepoxides are described in U.S. Pat. No. 4,681,811 at column 5, lines33 to 58, incorporated herein by reference.

Suitable curing agents for epoxy functional group-containing materialsinclude polyacid curing agents, such as the acid group-containingacrylic polymers prepared from an ethylenically unsaturated monomercontaining at least one carboxylic acid group and at least oneethylenically unsaturated monomer containing no carboxylic acid groups.Such acid functional acrylic polymers preferably have an acid numberanging from 30 to 150. Acid functional group-containing polyesters canbe used as well. The above-described polyacid curing agents aredescribed in further detail in U.S. Pat. No. 4,681,811 at column 6, line45 to column 9, line 54, incorporated herein by reference.

Also well known in the art as curing agents for isocyanate functionalgroup-containing materials are polyols, that is, materials having anaverage of two or more hydroxyl groups per molecule. Examples of suchmaterials suitable for use in the film-forming compositions of theinvention include polyalkylene ether polyols, including thio ethers;polyester polyols, including polyhydroxy polyesteramides; andhydroxyl-containing polycaprolactones and hydroxy-containing acrylicinterpolymers. Also useful are polyether polyols formed from theoxyalkylation of various polyols, for example, glycols such as ethyleneglycol, 1,6-hexanediol, Bisphenol A, and the like, or higher polyolssuch as trimethylolpropane, pentaerythritol, and the like. Polyesterpolyols can also be used. These and other suitable polyacid curingagents are described in U.S. Pat. No. 4,046,729 at column 7, line 52 tocolumn 8, line 9; column 8, line 29 to column 9, line 66; and U.S. Pat.No. 3,919,315 at column 2, line 64 to column 3, line 33, bothincorporated herein by reference. Polyamines can also be used as curingagents for isocyanate functional group-containing materials. Examples ofsuitable polyamine curing agents include primary or secondary diaminesor polyamines in which the radicals attached to the nitrogen atoms canbe saturated or unsaturated, aliphatic, alicyclic, aromatic,aromatic-substituted-aliphatic, aliphatic-substituted-aromatic, andheterocyclic. Exemplary suitable aliphatic, and alicyclic diaminesinclude 1,2-ethylene diamine, 1,2-propylene diamine, 1,8-methanediamine, isophorone diamine, propane-2,2-cyclohexyl amine, and the like.Suitable aromatic diamines include phenylene diamines and the toluenediamines, for example, o-phenylene diamine and p-tolylene diamine. Theseand other suitable polyamines described in detail in U.S. Pat. No.4,046,729 at column 6, line 61 to column 7, line 26, incorporated hereinby reference.

In a preferred embodiment, the transparent top coat is deposited from afilm-forming composition which further comprises, as component (c), oneor more polymers having reactive functional groups. The polymer (c)typically contains reactive functional groups selected from the groupconsisting of hydroxyl, carbamate, epoxy, isocyanate, carboxylic acidfunctional groups, and combinations or mixtures thereof. Hydroxyl and/orcarbamate functional group-containing polymers are preferred.

Suitable hydroxyl group-containing polymers (c) include acrylic polyols,polyester polyols, polyurethane polyols, polyether polyols, and mixturesthereof. Preferably the polymer (c) is an acrylic polyol having ahydroxyl equivalent weight ranging from 100 to 1000 grams perequivalent, preferably 150 to 500 grams per equivalent.

Suitable hydroxyl group and/or carboxyl group-containing acrylicpolymers can be prepared from polymerizable ethylenically unsaturatedmonomers, and are typically copolymers of (meth)acrylic acid and/orhydroxylalkyl esters of (meth)acrylic acid with one or more otherpolymerizable ethylenically unsaturated monomers such as alkyl esters of(meth)acrylic acid including methyl (meth)acrylate, ethyl(meth)acrylate, butyl (meth)acrylate and 2-ethyl hexylacrylate, andvinyl aromatic compounds such as styrene, alpha-methyl styrene and vinyltoluene. As used herein and in the claims, by “(meth)acrylate” and thelike terms is meant both acrylates and methacrylates.

Epoxy functional groups can be incorporated into the polymer preparedfrom polymerizable ethylenically unsaturated monomers by copolymerizingoxirane group-containing monomers, for example glycidyl (meth)acrylateand allyl glycidyl ether, with other polymerizable ethylenicallyunsaturated monomers, such as those discussed above. Preparation of suchepoxy functional acrylic polymers is described in detail in U.S. Pat.No. 4,001,156 at columns 3 to 6, incorporated herein by reference.

Carbamate functional groups can be incorporated into the polymerprepared from polymerizable ethylenically unsaturated monomers bycopolymerizing, for example, the above-described ethylenicallyunsaturated monomers with a carbamate functional vinyl monomer such as acarbamate functional alkyl ester of methacrylic acid. Useful carbamatefunctional alkyl esters can be prepared by reacting, for example, ahydroxyalkyl carbamate, such as the reaction product of ammonia andethylene carbonate or propylene carbonate, with methacrylic anhydride.Other useful carbamate functional vinyl monomers include, for instance,the reaction product of hydroxyethyl methacrylate, isophoronediisocyanate, and hydroxypropyl carbamate; or the reaction product ofhydroxypropyl methacrylate, isophorone diisocyanate, and methanol. Stillother carbamate functional vinyl monomers may be used, such as thereaction product of isocyanic acid (HNCO) with a hydroxyl functionalacrylic or methacrylic monomer such as hydroxyethyl acrylate, and thosedescribed in U.S. Pat. No. 3,479,328, incorporated herein by reference.Carbamate functional groups can also be incorporated into the acrylicpolymer by reacting a hydroxyl functional acrylic polymer with a lowmolecular weight alkyl carbamate such as methyl carbamate. Also,hydroxyl functional acrylic polymers can be reacted with isocyanic acidto provide pendent carbamate groups. Likewise, hydroxyl functionalacrylic polymers can be reacted with urea to provide pendent carbamategroups therefrom.

The polymers prepared from polymerizable ethylenically unsaturatedmonomers can be prepared by solution polymerization techniques, whichare well known to those skilled in the art, in the presence of suitablecatalysts such as organic peroxides or azo compounds, for example,benzoyl peroxide or N,N-azobis(isobutyronitrile). The polymerization canbe carried out in an organic solution in which the monomers are solubleby techniques conventional in the art. Alternatively, these polymers canbe prepared by aqueous emulsion or dispersion polymerization techniqueswhich are well known in the art. The ratio of reactants and reactionconditions are selected to result in an acrylic polymer with the desiredpendent functionality.

Polyester polymers are also useful in the film-forming compositions ofthe invention as the polymer (c). Useful polyester polymers typicallyinclude the condensation products of polyhydric alcohols andpolycarboxylic acids. Suitable polyhydric alcohols include ethyleneglycol, neopentyl glycol, trimethylolpropane, and pentaerythritol.Suitable polycarboxylic acids include adipic acid, 1,4-cyclohexyldicarboxylic acid, and hexahydrophthalic acid. Besides thepolycarboxylic acids mentioned above, functional equivalents of theacids such as anhydrides where they exist or lower alkyl esters of theacids such as the methyl esters can be used. Also, small amounts ofmonocarboxylic acids such as stearic acid can be used. The ratio ofreactants and reaction conditions are selected to result in a polyesterpolymer with the desired pendent functionality, i.e., carboxyl orhydroxyl functionality.

For example, hydroxyl group-containing polyesters can be prepared byreacting an anhydride of a dicarboxylic acid such as hexahydrophthalicanhydride with a diol such as neopentyl glycol in a 1:2 molar ratio.Where it is desired to enhance air-drying, suitable drying oil fattyacids may be used, and include those derived from linseed oil, soya beanoil, tall oil, dehydrated castor oil, or tung oil.

Carbamate functional polyesters can be prepared by first forming ahydroxyalkyl carbamate that can be reacted with the polyacids andpolyols used in forming the polyester. Alternatively, terminal carbamatefunctional groups can be incorporated into the polyester by reactingisocyanic acid with a hydroxy functional polyester. Also, carbamatefunctionality can be incorporated into the polyester by reacting ahydroxyl polyester with a urea. Additionally, carbamate groups can beincorporated into the polyester by a transcarbamylation reaction.Preparation of suitable carbamate functional group-containing polyestersis those described in U.S. Pat. No. 5,593,733 at column 2, line 40 tocolumn 4, line 9, incorporated herein by reference.

Polyurethane polymers containing terminal isocyanate or hydroxyl groupsalso can be used as the polymer (c) in the film-forming compositions ofthe invention. The polyurethane polyols or NCO-terminated polyurethaneswhich can be used are those prepared by reacting polyols includingpolymeric polyols with polyisocyanates. Polyureas containing terminalisocyanate or primary and/or secondary amine groups which also can beused are those prepared by reacting polyamines including polymericpolyamines with polyisocyanates. The hydroxyl/isocyanate oramine/isocyanate equivalent ratio is adjusted and reaction conditionsare selected to obtain the desired terminal groups. Examples of suitablepolyisocyanates include those described in U.S. Pat. No. 4,046,729 atcolumn 5, line 26 to column 6, line 28. Examples of suitable polyolsinclude those described in U.S. Pat. No. 4,046,729 at column 7, line 52to column 10, line 35. Examples of suitable polyamines include thosedescribed in U.S. Pat. No. 4,046,729 at column 6, line 61 to column 7,line 32 and in U.S. Pat. No. 3,799,854 at colurnn 3, lines 13 to 50,both incorporated herein by reference.

Carbamate functional groups can be introduced into the polyurethanepolymers by reacting a polyisocyanate with a polyester having hydroxylfunctionality and containing pendent carbamate groups. Alternatively,the polyurethane can be prepared by reacting a polyisocyanate with apolyester polyol and a hydroxyalkyl carbamate or isocyanic acid asseparate reactants. Examples of suitable polyisocyanates are aromaticisocyanates, such as 4,4′-diphenylmethane diisocyanate, 1,3-phenylenediisocyanate, and toluene diisocyanate, and aliphatic polyisocyanates,such as 1,4-tetramethylene diisocyanate and 1,6-hexamethylenediisocyanate. Cycloaliphatic diisocyanates, such as 1,4-cyclohexyldiisocyanate and isophorone diisocyanate also can be employed.

Examples of suitable polyether polyols include polyalkylene etherpolyols such as those having the following structural formula:

where the substituent R is hydrogen or a lower alkyl group containingfrom 1 to 5 carbon atoms including mixed substituents, and n has a valuetypically ranging from 2 to 6 and m has a value ranging from 8 to 100 orhigher. Exemplary polyalkylene ether polyols includepoly(oxytetramethylene) glycols, poly(oxytetraethylene) glycols,poly(oxy-1,2-propylene) glycols, and poly(oxy-1,2-butylene) glycols.

Also useful are polyether polyols formed from oxyalkylation of variouspolyols, for example, glycols such as ethylene glycol, 1,6-hexanediol,Bisphenol A and the like, or other higher polyols such astrimethylolpropane, pentaerythritol, and the like. Polyols of higherfunctionality which can be utilized as indicated can be made, forinstance, by oxyalkylation of compounds such as sucrose or sorbitol. Onecommonly utilized oxyalkylation method is reaction of a polyol with analkylene oxide, for example, propylene or ethylene oxide, in thepresence of an acidic or basic catalyst. Specific examples of polyethersinclude those sold under the names TERATHANE and TERACOL, available fromE. I. Du Pont de Nemours and Company, Inc.

Generally, the polymers having reactive functional groups (c) useful inthe film-forming compositions of the invention have a weight averagemolecular weight (Mw) typically ranging from 1000 to 20,000, preferably1500 to 15,000, and more preferably 2000 to 12,000 as determined by gelpermeation chromatography using a polystyrene standard.

The polymer having reactive functional groups (c), when employed, can bepresent in the film-forming compositions of the invention in an amountof at least 0 to 80 percent by weight, preferably at least 5 to 60percent by weight, and more preferably at least 10 to 50 percent byweight based on weight of total resin solids in the film-formingcomposition. Also, the polymer having reactive functional groups (c) ispresent in the film-forming compositions of the invention in an amounttypically less than 80 percent by weight, preferably less than 60 to 5percent by weight, and more preferably less than 50 to 10 percent byweight based on weight of total resin solids in the film-formingcomposition. The amount of the polymer having reactive functional groups(c) present in the film-forming compositions of the invention may rangebetween any combination of these values inclusive of the recited values.

It should be mentioned that when both the polysiloxane (a) and thepolymer (c) are present, the reactive functional groups of (a) and (c)can be the same or different so long as both contain reactive functionalgroups which are reactive with the functional groups of the curing agent(b).

The components (a), (b) and, if employed, (c) which comprise theinventive film-forming compositions, are generally dissolved ordispersed in an organic solvent. Suitable organic solvents include, forexample, alcohols, ketones, aromatic hydrocarbons, glycol ethers,esters, or mixtures thereof. In solvent based coating compositions, theorganic solvent typically is present in amounts ranging from 5 to 80percent by weight based on total weight of the composition.

The film-forming composition preferably also contains a catalyst toaccelerate the cure reaction, for example, between the aminoplast curingagent and the reactive hydroxyl and/or carbamate functional groups ofthe polysiloxane (a) and, if present, the polymer (c). Examples ofsuitable catalysts include acidic materials, for example, acidphosphates, such as phenyl acid phosphate, and substituted orunsubstituted sulfonic acids such as dodecylbenzene sulfonic acid orparatoluene sulfonic acid. The catalyst usually is present in an amountranging from 0.1 to 5.0 percent by weight, preferably 0.5 to 1.5 percentby weight, based on the total weight of resin solids.

Optional ingredients, for example, plasticizers, surfactants,thixotropic agents, anti-gassing agents, organic cosolvents, flowcontrollers, anti-oxidants, UV light absorbers, and similar additivesconventional in the art can be included in the composition. Theseingredients typically are present in an amount of up to about 40 percentby weight based on the total weight of resin solids.

The film-forming composition of the present invention can besolvent-borne or water-borne. Preferably, the composition issolvent-borne. Suitable solvent carriers include the various alcohols,esters, ethers, aromatic solvents, and other solvents, includingmixtures thereof, as are known in the art of coating formulation. Thefilm-forming composition typically has a total solids content of 40 to75 percent by weight based on total weight of the film-formingcomposition. Alternatively, the inventive film-forming composition canbe in a solid particulate form suitable for use as powder coating.

In a preferred embodiment of the invention, the transparent top coat isdeposited from a film-forming composition which further comprisessubstantially inorganic microparticles which are dispersed in thefilm-forming composition. The inorganic microparticles, prior todispersion, have an average diameter ranging from 1 to 1000 nanometers,preferably from 2 to 200 nanometers, and more preferably from 4 to 50nanometers. Prior to incorporation, the preferred inorganicmicroparticles are in the form of a sol, preferably an organosol, of themicroparticles.

The substantially inorganic microparticles suitable for use in thefilm-forming compositions of the invention can comprise, for example, acore of essentially a single inorganic oxide such as silica incolloidal, filmed, or amorphous form; alumina; or an inorganic oxide ofone type on which is deposited an inorganic oxide of another type. Thesuitable substantially inorganic microparticles, however, must besubstantially colorless so as to not seriously interfere with the lighttransmissive properties of the transparent film-forming composition ofthe present invention. Suitable inorganic microparticles includecolloidal silicas, such as those commercially available from NissanChemical Company under the tradename ORGANOSILICASOLS and from ClariantCorporation under the tradename HIGHLINK, colloidal alumina available asNALCO 8676 from Nalco Chemical, and colloidal zirconia available asHIT-32M from Nissan Chemical Company.

Additionally, it should be understood that although the substantiallyinorganic microparticles may be discrete or associated through physicaland/or chemical means into aggregates, and although a given sample ofthe microparticles generally will have particles falling into a range ofparticle sizes, the substantially inorganic microparticles preferablyhave an average diameter in the range of from 1 to 150 nanometers. Priorto incorporation, the microparticles used as starting material should bein a form which will permit the formation of a stable dispersion in thefilm-forming composition.

As used herein, by “stable dispersion” is meant that the substantiallyinorganic microparticles remain uniformly suspended throughout theliquid phase of the film-forming coating composition. Upon standing atambient conditions of temperature and pressure, the dispersions do notflocculate or form a hard sediment. If over time some sedimentationoccurs, it can be easily redispersed with low shear stirring usingconventional paint mixing techniques.

A particularly desirable class of substantially inorganic microparticlesinclude sols of a wide variety of small-particle, colloidal silicashaving an average diameter of from 1 to 1000 nanometers, preferably from2 to 200 nanometers, and more preferably from 4 to 50 nanometers, whichsilicas have been surface modified during and/or after the particles areinitially formed. Such materials can be prepared by a variety oftechniques in various forms, examples of which include organosols andmixed sols. As used herein the term “mixed sols” is intended to includethose dispersions of colloidal silica in which the dispersing mediumcomprises both an organic liquid and water. Such small particlecolloidal silicas are readily available, are essentially colorless, andhave refractive indices which permit their inclusion in transparentcoating compositions.

Such surface modified silicas include common colloidal forms havingultimate particles of silica which, at least prior to incorporation inthe coating composition, may contain on the surface chemically bondedcarbon-containing moieties, as well as such groups as anhydrous SiO₂groups and SiOH groups, various ionic groups physically associated orchemically bonded within the surface of the silica, adsorbed organicgroups and combinations thereof, depending on the characteristics of theparticular silica desired.

The microparticles can be reactive with the binder either by theirinherent reactivity (e.g., via the presence of SiOH groups) or thisreactivity can be converted using one of a wide range of alkoxy silanecoupling agents (e.g., glycidyl alkoxy silanes, isocyanate alkoxysilanes, amino alkoxy silanes, and carbamyl alkoxy silanes). Thereactive groups on the silica allow the silica to be reactive with thereactive groups of the film-forming polymer(s) without additionaltreatment when suitable curing agent is used. Where the silica surfaceis non-reactive with the reactive groups of the film-forming polymer(s)or curing agent(s), the inorganic particles can be reacted with acoupling agent which comprises a compound having a functionality capableof covalently bonding to the inorganic particles and having afunctionality capable of crosslinking with the reactive groups of thefilm-forming polymer(s) where both functionalities are reacted onto abackbone of the coupling agent. The backbone of the coupling agent is apolyvalent linking group. Examples of the polyvalent linking groupinclude polyvalent radicals such as silicone and phosphorous, alkylgroups, oligomers or polymers such as acrylic, urethane, polyester,polyamide, epoxy, urea, and alkyd oligomers and polymers. Examples ofthe functionality that reacts with the inorganic particle includehydroxyl, hydroxy ether, phenoxy, silane, and aminoplast functionalites.The above-described surface-modified silicas are described in detail inU.S. Pat. No. 5,853,809 at column 6, line 51 to column 8, line 43,incorporated herein by reference.

As aforementioned, the multi-component composite coating compositions ofthe present invention comprise a pigmented film-forming compositionserving as a base coat (i.e., a color coat) and a film-formingcomposition applied over the color coat serving as a transparent topcoat(i.e., a clear coat). The base coat and clear coat compositions used inthe multi-component composite coating compositions of the invention arepreferably formulated into liquid high solids coating compositions, thatis, compositions containing 40 percent, preferably greater than 50percent by weight resin solids. The solids content is determined byheating a sample of the composition to 105° to 110° C. for 1 to 2 hoursto drive off the volatile material, and subsequently measuring relativeweight loss. Although the compositions are preferably liquid coatingcompositions, they can also be formulated as powder coatingcompositions.

The film-forming composition of the base coat in the color-plus-clearsystem can be any of the compositions useful in coatings applications,particularly automotive applications. The film-forming composition ofthe base coat comprises a resinous binder and a pigment to act as thecolorant. Particularly useful resinous binders are acrylic polymers,polyesters, including alkyds, and polyurethanes.

The resinous binders for the base coat can be organic solvent-basedmaterials such as those described in U.S. Pat. No. 4,220,679, notecolumn 2, line 24 continuing through column 4, line 40. Also,water-based coating compositions such as those described in U.S. Pat.No. 4,403,003, U.S. Pat. No. 4,147,679 and U.S. Pat. No. 5,071,904 canbe used as the binder in the base coat composition.

The base coat composition contains pigments as colorants. Suitablemetallic pigments include aluminum flake, copper bronze flake and metaloxide coated mica. Besides the metallic pigments, the base coatcompositions can contain non-metallic color pigments conventionally usedin surface coatings including inorganic pigments such as titaniumdioxide, iron oxide, chromium oxide, lead chromate, and carbon black;and organic pigments such as phthalocyanine blue and phthalocyaninegreen.

Optional ingredients in the base coat composition include those whichare well known in the art of formulating surface coatings and includesurfactants, flow control agents, thixotropic agents, fillers,anti-gassing agents, organic co-solvents, catalysts, and other customaryauxiliaries. Examples of these materials and suitable amounts aredescribed in U.S. Pat. No. 4,220,679, U.S. Pat. No. 4,403,003, U.S. Pat.No. 4,147,769 and U.S. Pat. No. 5,071,904.

The base coat compositions can be applied to the substrate by anyconventional coating technique such as brushing, spraying, dipping orflowing, but they are most often applied by spraying. The usual spraytechniques and equipment for air spraying, airless spray andelectrostatic spraying in either manual or automatic methods can beused.

During application of the base coat to the substrate, the film thicknessof the base coat formed on the substrate is typically 0.1 to 5 mils(about 2.54 to about 127 microns), preferably 0.1 to 2 mils (about 2.54to about 50.4 microns).

After forming a film of the base coat on the substrate, the base coatcan be cured or alternatively given a drying step in which solvent isdriven out of the base coat film by heating or an air drying periodbefore application of the clear coat. Suitable drying conditions willdepend on the particular base coat composition, and on the ambienthumidity if the composition is water-borne, but in general, a dryingtime of from about 1 to 15 minutes at a temperature of about 75° to 200°F. (21° to 93° C.) will be adequate.

The transparent top coat (or clear coat) composition is typicallyapplied to the base coat by spray application, however, the top coat canbe applied by any conventional coating technique as described above. Anyof the known spraying techniques can be used such as compressed airspraying, electrostatic spraying, and either manual or automaticmethods. As mentioned above, the clear top coat can be applied to acured or dried base coat before the base coat has been cured. In thelatter instance, the two coatings are then heated to cure both coatinglayers simultaneously. Typical curing conditions range from 100° to 475°F. (39° to 246° C.) for 1 to 30 minutes. The clear coating thickness(dry film thickness) is typically 1 to 6 mils (about 25.4 to about 152.4microns).

In an alternative embodiment of the invention, a second top coatfilm-forming composition is applied to the first top coat to form a“clear-on-clear” top coat. The first top coat film-forming compositionis applied over the base coat as described above. The second top coatfilm-forming composition can be applied to a cured or to a dried firsttop coat before the base coat and first top coat have been cured, i.e.,a wet-on-wet” application. The base coat, the first top coat and thesecond top coat can then be heated to cure the three coatingssimultaneously.

It should be understood that the second transparent top coat and thefirst transparent top coat film-forming compositions can be the same ordifferent provided that, when applied wet-on-wet, one top coat does notsubstantially interfere with the curing of the other. The firsttransparent top coat film-forming composition can be virtually anytransparent top coating film-forming composition known to those skilledin the art. The first transparent top coat composition can bewater-borne or solventborne, or, alternatively, in solid particulateform, i.e., a powder coating. Preferably it is solventborne.

Examples of suitable first top coating compositions includecrosslinkable film-forming compositions comprising at least onethermosettable film-forming material and at least one curing agent.Suitable waterborne clearcoats are disclosed in U.S. Pat. No. 5,098,947(incorporated by reference herein) and are based on water solubleacrylic resins. Useful solvent borne clearcoats are disclosed in U.S.Pat. Nos. 5,196,485 and 5,814,410 (incorporated by reference herein) andinclude polyepoxides and polyacid curing agents. Suitable powderclearcoats are described in U.S. Pat. No. 5,663,240 (incorporated byreference herein) and include epoxy functional acrylic copolymers andpolycarboxylic acid curing agents.

Typically, after forming the first top coat over the base coat, thefirst top coat is given a drying step in which solvent is driven out ofthe film by heating or, alternatively, an air drying period beforeapplication of the second top coat. Suitable drying conditions willdepend on the particular first top coat composition, and on the ambienthumidity if the composition is water-borne, but, in general, a dryingtime from 1 to 15 minutes at a temperature of 75° to 200° F. (21° to 93°C.) will be adequate.

The second top coat film-forming composition can be applied as describedabove for the first top coat by any conventional coating applicationtechnique. Typical curing conditions are those described above for thetop coat. The second top coating dry film thickness typically rangesfrom 0.3 to 3 mils (7.5 micrometers to 75 micrometers), preferably from0.5 to 2 mils (12.5 micrometers to 50 micrometers).

The multi-component composite coating compositions can be applied overvirtually any substrate including wood, metals, glass, cloth, plastic,foam, including elastomeric substrates and the like. They areparticularly useful in applications over metals and elastomericsubstrates that are found on motor vehicles where they exhibit excellentappearance properties and improved mar and scratch resistance propertiesas evaluated by measuring the gloss of coated substrates before andafter abrading of the coated substrates using a consistent laboratorymethod.

Illustrating the invention are the following examples which, however,are not to be considered as limiting the invention to their details.Unless otherwise indicated, all parts and percentages in the followingexamples, as well as throughout the specification, are by weight.

EXAMPLES

Examples A and B describe the preparation of a chain-extended disiloxanepolyol and a pentasiloxane polyol, respectively, which are useful in thefilm-forming compositions of the invention. Comparative Example Idescribes the preparation of a control film-forming composition whichuses a conventional acrylic polyol (as opposed to the inventivepolysiloxane polyols) and an aminoplast curing agent. Examples 2 and 3describe the preparation of analogous film-forming compositions of thepresent invention which contain the polysiloxane polyols of Examples Aand B, respectively.

Example A

This example describes the preparation of a chain-extended disiloxanepolyol used in the film-forming compositions of the present invention.The disiloxane polyol was prepared as follows: To a suitable reactionvessel flushed with N₂ was added 930.0 g of trimethylolpropane diallylether and 1.2085 mL of karsted catalyst. Over the following 4 hourperiod, 698.8 g of 1,1,3,3-tetramethyl disiloxane was added to thereaction mixture and the temperature was increased and held atapproximately 50° C. When about half of the total amount oftrimethylolpropane diallyl ether had been added, 198.4 g of allylglycidyl ether was added over a period of about 4 hours. When theadditions were complete, the reaction was held for 2 hours at which time71.4 g of allyl glycidyl ether were added over a period of 0.5 hour. Thereaction temperature was maintained at 50° C. for an additional 2 hourswhile the reaction was monitored by infrared spectroscopy fordisappearance of the silicon hydride absorption band (Si—H, 2150 cm⁻¹).The reaction temperature was cooled to ambient temperature at which time258.7 g of diethanolamine was added. The temperature was increased to125° C. and the reaction mixture was maintained at that temperature fora period of about 2 hours.

Example B

This example describes the preparation of a chain-extended pentasiloxanepolyol used in the film-forming compositions of the present invention.The pentasiloxane polyol was prepared as follows: To a suitable reactionvessel flushed with N₂ was added 62.0 of trimethylolpropane diallylether, 0.1418 mL of karsted catalyst and 65.5 g allyl glycidyl ether.Over a period of 1 hour, 135.4 g of pentasiloxane available as MASILWAXBASE from BASF Corporation was added to the reaction mixture as thetemperature increased to and was maintained at 50° C. At the completionof the addition, the reaction was held for 2.5 hours, at which time0.0709 mL of karsted catalyst was added to the reaction mixture and thereaction was monitored by infrared spectroscopy for disappearance of thesilicon hydride absorption band (Si—H, 2150 cm⁻¹). The temperature wasmaintained at 50° C. for an additional 2 hours, at which time 60.2 g ofdiethanolamine was added. The temperature was then increased to 125° C.and held for a period of 2 hours.

Comparative Example 1

This comparative example describes the preparation of a high solidsfilm-forming composition used to form a transparent top coat in amulti-component composite coating. The film-forming composition wasprepared from a mixture of the following ingredients:

Ingredients Resin Solids Weight in Grams Methyl Amyl Ketone — 30.00TINUVIN 928¹ 1.50 1.50 TINUVIN 328² 1.50 1.50 TINUVIN 123³ 1.00 1.00Acrylic polyol resin⁴ 50.00 71.43 CYMEL 202⁵ 50.00 62.50Polybutylacrylate⁶ 0.30 0.50 Acid Catalyst⁷ 1.00 1.33¹2-(2H-Benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)4-(1,1,3,3-tetramethylbutyl)phenolUV lightstabilizer available from Ciba-Geigy Corp.²2-(2′-Hydroxy-3′,5′-ditert-amylphenyl)benzotriazole UV light stabilizeravailable from Ciba-Geigy Corp. ³Sterically hindered amino ether lightstabilizer available from Ciba-Geigy Corp. ⁴Copolymer comprising (18%butyl methacrylate/40% hydroxy-propylmethacrylate/1% methylmethacrylate/20% styrene/19% butyl acrylate/2% acrylic acid) 71% solidsin a solvent blend of (55% xylene/45% aromatic hydrocarbon) ⁵High imino,methylated/butylated melamine formaldehyde resin available from CYTECIndustries, Inc. ⁶Polybutylacrylate, 60 percent solids in xylene.⁷Phenyl acid phosphate, 75 percent solids in isopropanol.

Example 2

This example describes the preparation of a film-forming compositionused to form the transparent top coat in the multi-component compositecoating compositions of the present invention. The composition containsthe chain-extended disiloxane of Example A. The film-forming compositionwas prepared from a mixture of the following ingredients:

Ingredients Resin Solids Weight in Grams Methyl Amyl Ketone — 30.00TINUVIN 928 1.50 1.50 TINUVIN 328 1.50 1.50 TINUVIN 123 1.00 1.00Polysiloxane of Example A 50.00 51.56 CYMEL 202 50.00 62.50 Flowadditive of Example 1 0.30 0.50 Acid Catalyst of Example 1 1.00 1.33

Example 3

This example describes the preparation of a film-forming composition ofthe invention which contains the chain-extended pentasiloxane of ExampleB. The film-forming composition was prepared from a mixture of thefollowing ingredients:

Ingredients Resin Solids Weight in Grams Methyl Amyl Ketone — 30.00TINUVIN 928 1.50 1.50 TINUVIN 328 1.50 1.50 TINUVIN 123 1.00 1.00Polysiloxane of Example B 50.00 61.05 CYMEL 202 50.00 62.50 Flowadditive of Example 1 0.30 0.50 Acid Catalyst of Example 1 1.00 1.33

Each of the film-forming compositions of Examples 1 through 3 above wereprepared as one-pack systems by sequentially adding the listedingredients and mixing under mild agitation. Test panels were preparedas described below.

TEST PANEL PREPARATION:

BWB-5555 black waterbome basecoat (commercially available from PPGIndustries, Inc.) was spray applied to steel panels supplied by ACTLaboratories, Inc. which had been pre-coated with ED5000 cationicelectrodepositable primer (commercially available from PPG Industries,Inc.) and GPXH5379 Primer Surfacer. The base coated panels werepre-baked for 5 minutes at 200° F. The resulting base coat dry filmthickness was approximately 0.6 mils.

Each of the film-forming compositions of Examples 1 through 3 above wasspray applied as a transparent top coat to the base coated panels toform thereon a transparent top coat having a dry film thickness ofapproximately 1.8 mils. The top coated panels were allowed to “flash” atambient temperatures for approximately 10 minutes, then thermally curedat 285° F. for 30 minutes. The multi-component composite coatings weretested for various physical properties including gloss, scratchresistance, and hardness.

TEST PROCEDURES:

Scratch resistance of coated test panel was measured using the followingmethod: Initial 20° gloss of the coated panels was measured using aNOVO-GLOSS 20 statistical glossmeter, available from Paul N. GardnerCompany, Inc. Coated panels were subjected to scratch testing bylinearly scratching the coated surface with a weighted abrasive paperfor ten double rubs using an Atlas AATCC Scratch Tester, Model CM-5,available from Atlas Electrical Devices Company of Chicago, Ill. Panelswere then rinsed with water and carefully patted dry. The 20° speculargloss was measured on the scratched area of each test panel. The numberreported is the percent of the initial gloss retained after scratchtesting, i.e., 100× scratched gloss/initial gloss.

Film hardness of the multi-layer composite coatings was measured using aTUKON Hardness tester to determine Knoop Hardness values according toASTM-D1474-92. A higher reported value indicates a harder coatingsurface. Test results are provided in the following Table 1.

TABLE 1 % 20° Gloss Initial After Scratch Knoop Example 20° Gloss TestHardness 1 96 68% 13.0 (Comparative) 2 92 93% 6.0 3 92 97% 10.2

The data reported in Table 1 above illustrate that the multi-componentcomposite coating compositions of the invention which contain thechain-extended polysiloxane polyols provide coatings having improvedscratch resistance.

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications which are within the spirit and scopeof the invention, as defined by the appended claims.

We claim:
 1. A multi-component composite coating composition comprisinga base coat deposited from a pigmented film-forming composition and atransparent top coat applied over the base coat in which the transparenttop coat is deposited from a film-forming composition comprising: (a) anungelled organic polysiloxane having reactive functional groups, saidpolysiloxane comprising at least one unit of the following structure(I):

 wherein R¹ and R² are independently selected from the group consistingof OH and monovalent hydrocarbon groups; which optionally contains oneor more reactive functional groups, wherein the polyvalent linking groupis X is an organic polyvalent linking group selected from the groupconsisting of alkylene, oxyalkylene, and alkylene aryl, and X is derivedfrom a material having two or more unsaturated bonds capable ofundergoing hydrosilylation reaction; and n has a value ranging from 2 to4 such that n is equal to the number of unsaturated bonds capable ofundergoing hydrosilylation reaction; and (b) a curing agent havingfunctional groups reactive with the functional groups of (a).
 2. Themulti-component composite coating composition of claim 1, wherein Xcontains reactive functional groups.
 3. The multi-component compositecoating composition of claim 1, wherein the reactive functional groupsof the polysiloxane (a) are selected from the group consisting ofhydroxyl, carbamate, epoxy, isocyanate, and carboxylic acid functionalgroups.
 4. The multi-component composite coating composition of claim 3,wherein the reactive functional groups of the polysiloxane (a) comprisehydroxyl functional groups.
 5. The multi-component composite coatingcomposition of claim 4, wherein the polysiloxane (a) is the ungelledreaction product of the following reactants: (a) a polysiloxanecontaining silicon hydride having the structure (II):

 wherein the R groups are independently selected from the groupconsisting of H, OH, and monovalent hydrocarbon groups connected to thesilicon atoms, provided that at least one of the groups represented by Ris H; and m ranges from 0 to 100, such that the mole percent ofhydrogen-bonded silicon atoms to non-hydrogen-bonded silicon atomsranges from 10 to 100; and (b) a hydroxyl functional group-containingmaterial having two or more unsaturated bonds capable of undergoinghydrosilylation reaction.
 6. The multi-component composite coatingcomposition of claim 5, wherein m ranges from 0 to
 5. 7. Themulti-component composite coating composition of claim 5, wherein thereactant (b) is a hydroxyl functional group-containing polyallyl ether.8. The multi-component composite coating composition of claim 7, whereinthe hydroxyl functional group-containing polyallyl ether is selectedfrom the group consisting of trimethylolpropane diallyl ether,pentaerythritol diallyl ether, pentaerythritol triallyl ether andmixtures thereof.
 9. The multi-component composite coating compositionof claim 5, wherein the equivalent ratio of Si—H to total unsaturationcapable of undergoing hydrosilylation reaction is 0.5 to 2:1.
 10. Themulti-component composite coating composition of claim 5, wherein thepolysiloxane has an OH equivalent weight ranging from 50 to 500 gramsper equivalent.
 11. The multi-component composite coating composition ofclaim 3, wherein the reactive functional groups of the polysiloxane (a)comprise carbamate functional groups.
 12. The multi-component compositecoating composition of claim 11, wherein the polysiloxane (a) is theungelled reaction product of the following reactants: (a) a polysiloxanecontaining silicon hydride having the structure (II):

 wherein the R groups are independently selected from the groupconsisting of H, OH, and monovalent hydrocarbon groups connected to thesilicon atoms, provided that at least one of the groups represented by Ris H; and m ranges from 0 to 100, such that the mole percent ofhydrogen-bonded silicon atoms to non-hydrogen-bonded silicon atomsranges from 10 to 100; (b) a hydroxyl functional group-containingmaterial having two or more unsaturated bonds capable of undergoinghydrosilylation reaction; and (c) a low molecular weight carbamatefunctional material.
 13. The multi-component composite coatingcomposition of claim 12, wherein the low molecular weight carbamatefunctional material (c) comprises the reaction product of the followingreactants: (a) an alcohol or glycol ether; and (b) a urea.
 14. Themulti-component composite coating composition of claim 12, wherein mranges from 0 to
 5. 15. The multi-component composite coatingcomposition of claim 12, wherein the reactant (b) is a hydroxylfunctional group-containing polyallyl ether.
 16. The multi-componentcomposite coating composition of claim 15, wherein the hydroxylfunctional group-containing polyallyl ether is selected from the groupconsisting of trimethylolpropane diallyl ether, pentaerythritol diallylether, and pentaerythritol triallyl ether, Bisphenol A diallyl ether andmixtures thereof.
 17. The multi-component composite coating compositionof claim 12, wherein the equivalent ratio of Si—H to total unsaturationcapable of undergoing hydrosilylation reaction ranges from 0.5 to 2:1.18. The multi-component composite coating composition of claim 4,wherein the curing agent comprises an aminoplast.
 19. Themulti-component composite coating composition of claim 18, wherein thecuring agent further comprises a polyisocyanate.
 20. The multi-componentcomposite coating composition of claim 19, further comprising an acidcatalyst.
 21. The multi-component composite coating composition of claim11, wherein the curing agent comprises an aminoplast.
 22. Themulti-component composite coating composition of claim 21, wherein thecuring agent further comprises a polyisocyanate.
 23. The multi-componentcomposite coating composition of claim 22, further comprising an acidcatalyst.
 24. The multi-component composite coating composition of claim1, wherein said film-forming composition further comprises (c) a polymerhaving reactive functional groups.
 25. The multi-component compositecoating composition of claim 24, wherein the polymer (c) comprisesreactive functional groups selected from the group consisting ofhydroxyl, carbamate, epoxy, isocyanate, epoxy, and carboxylic acidfunctional groups.
 26. The multi-component composite coating compositionof claim 25, wherein the polymer (c) contains reactive functional groupsselected from the group consisting of hydroxyl groups, carbamate groupsand mixtures thereof.
 27. The multi-component composite coatingcomposition of claim 25, wherein the polymer (c) contains hydroxylfunctional groups.
 28. The multi-component composite coating compositionof claim 27, wherein the polymer (c) is selected from the groupconsisting of acrylic polyols, polyester polyols, polyurethane polyols,and polyether polyols.
 29. The multi-component composite coatingcomposition of claim 28, wherein the polymer (c) is an acrylic polyolhaving a hydroxyl equivalent weight ranging from 100 to 1000 grams perequivalent.
 30. A multi-component composite coating compositioncomprising a base coat deposited from a pigmented film-formingcomposition and a transparent top coat applied over the base coat inwhich the transparent top coat is deposited from a film-formingcomposition comprising: (a) 2 to 90 weight percent based on weight oftotal resin solids of an ungelled organic polysiloxane having hydroxylfunctional groups, said polysiloxane comprising at least one unit of thefollowing structure (I):

 wherein R¹ and R² are independently selected from the group consistingof OH and monovalent hydrocarbon groups; X′ is a hydroxyl functionalgroup-containing organic polyvalent linking group selected from thegroup consisting of alkylene, oxyalkylene, and alkylene aryl, and isderived from a hydroxyl group-containing polyallyl ether capable ofundergoing hydrosilylation reaction, said polysiloxane having an OHequivalent weight of 50 to 500 grams per equivalent; and n has a valueranging from 2 to 4 such that n is equal to the number of unsaturatedbonds capable of undergoing hydrosilylation reaction; (b) 2 to 80 weightpercent based on weight of total resin solids of an acrylic polyolhaving an OH equivalent weight of 100 to 1000 grams per equivalent; and(c) 2 to 60 weight percent based on weight of total resin solids of anaminoplast-curing agent.
 31. The multi-component composite coatingcomposition of claim 30 further comprising 5 to 65 weight percent basedon weight of total resin solids of a polyisocyanate-curing agent.
 32. Amulti-component composite coating composition comprising a base coatdeposited from a pigmented film-forming composition and a transparenttop coat applied over the base coat in which the transparent top coat isdeposited from a film-forming composition comprising: (a) 2 to 90 weightpercent based on weight of total resin solids of an ungelled organicpolysiloxane having carbamate functional groups, said polysiloxanecomprising at least one unit of the following structure (I):

 wherein R¹ and R² are independently selected from the group consistingof OH and monovalent hydrocarbon groups; X″ is a carbamate functionalgroup-containing organic polyvalent linking group selected from thegroup consisting of alkylene, oxyalkylene, and alkylene aryl, and isderived from a hydroxyl group-containing polyallyl ether capable ofundergoing hydrosilylation reaction; and n has a value ranging from 2 to4 such that n equals the number of unsaturated bonds capable ofundergoing hydrosilylation reaction; (b) 2 to 80 weight percent based onweight of total resin solids of an acrylic polyol having an OHequivalent weight of 100 to 1000 grams per equivalent; and (c) 2 to 60weight percent based on weight of total resin solids of anaminoplast-curing agent.
 33. The multi-component composite coatingcomposition of claim 32, wherein the film-forming composition furthercomprises 5 to 65 weight percent based on weight of total resin solidsof a polyisocyanate-curing agent.
 34. A process for applying amulti-component composite coating to a substrate comprising thefollowing steps: (a) applying to a substrate a pigmented film-formingcomposition from which a base coat is deposited onto the substrate; and(b) applying onto the base coat a film-forming composition from which atransparent top coat is deposited over the base coat, said film-formingcomposition comprising: (i) an ungelled organic polysiloxane havingreactive functional groups, said polysiloxane comprising at least oneunit of the following structure (I):

 wherein R¹ and R² are independently selected from the group consistingof OH and monovalent hydrocarbon groups; X is an organic polyvalentlinking group which optionally contains one or more reactive functionalgroups, wherein the polyvalent linking group is selected from the groupconsisting of alkylene, oxyalkylene, and alkylene aryl, and X is derivedfrom a material having two or more unsaturated bonds capable ofundergoing hydrosilylation reaction; and n has a value ranging from 2 to4 such that n is equal to the number of unsaturated bonds capable ofundergoing hydrosilylation reaction; and (ii) a curing agent havingfunctional groups reactive with the functional groups of (i).
 35. Asubstrate coated by the process of claim
 34. 36. A substrate coated withthe multi-component composite coating composition of claim
 1. 37. Amulti-component composite coating composition comprising a base coatdeposited from a pigmented film-forming composition, a first transparenttop coat applied over the base coat in which the transparent top coat isdeposited from a first film-forming composition, and a secondtransparent top coat applied over the first transparent top coat inwhich the second transparent top coat is deposited from a secondfilm-forming composition comprising: (a) an ungelled organicpolysiloxane having reactive functional groups, said polysiloxanecomprising at least one unit of the following structure (I):

 wherein R¹ and R² are independently selected from the group consistingof OH and monovalent hydrocarbon groups; X is an organic polyvalentlinking group which optionally contains one or more reactive functionalgroups, wherein the polyvalent linking group is selected from the groupconsisting of alkylene, oxyalkylene, and alkylene aryl, and X is derivedfrom a material having two or more unsaturated bonds capable ofundergoing hydrosilylation reaction; and n has a value ranging from 2 to4 such that n is equal to the number of unsaturated bonds capable ofundergoing hydrosilylation reaction; and (b) a curing agent havingfunctional groups reactive with the functional groups of (a).
 38. Themulti-component composite coating composition of claim 37, wherein Xcontains reactive functional groups.
 39. The multi-component compositecoating composition of claim 37, wherein the reactive functional groupsof the polysiloxane (a) are selected from the group consisting ofhydroxyl, carbamate, urea, urethane, alkoxysilane, epoxy, isocyanate andblocked isocyanate and carboxylic acid functional groups.
 40. Themulti-component composite coating composition of claim 39, wherein thereactive functional groups of the polysiloxane (a) comprise hydroxylfunctional groups, carbamate functional groups and mixtures thereof. 41.A process for applying a multi-component composite coating to asubstrate comprising the following steps: (a) applying to a substrate apigmented film-forming composition from which a base coat is depositedonto the substrate; (b) applying onto the base coat a first top coatfilm-forming composition from which a transparent top coat is depositedover the base coat; (c) applying onto the first top coat a secondfilm-forming composition from which a second top coat is deposited, saidsecond film-forming composition comprising: (i) an ungelled organicpolysiloxane having reactive functional groups, said polysiloxanecomprising at least one unit of the following structure (I):

 wherein R¹ and R² are independently selected from the group consistingof OH and monovalent hydrocarbon groups; X is an organic polyvalentlinking group which optionally contains one or more reactive functionalgroups, wherein the polyvalent linking group is selected from the groupconsisting of alkylene, oxyalkylene, and alkylene aryl, and X is derivedfrom a material having two or more unsaturated bonds capable ofundergoing hydrosilylation reaction; and n has a value ranging from 2 to4 such that n is equal to the number of unsaturated bonds capable ofundergoing hydrosilylation reaction; and (ii) a curing agent havingfunctional groups reactive with the functional groups of (i).
 42. Asubstrate coated by the process of claim
 41. 43. A substrate coated withthe multi-component composite coating composition of claim
 37. 44. Acurable composition comprising the following components: (a) at leastone ungelled organic polysiloxane having reactive functional groups,said polysiloxane comprising at least one unit of the structure (I):

 wherein R¹ and R² are independently selected from the group consistingof OH and monovalent hydrocarbon groups; X is an organic polyvalentlinking group which optionally contains one or more reactive functionalgroups, wherein the polyvalent linking group is selected from the groupconsisting of alkylene, oxyalkylene and alkylene aryl which X is derivedfrom an organic material having two or more unsaturated bonds capable ofundergoing hydrosilylation reaction; and n has a value ranging from 2 to4 such that n is equal to the number of unsaturated bonds capable ofundergoing hydrosilylation reaction; and (b) at least one curing agenthaving functional groups reactive with the functional groups of (a).